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Python Precedence and Associativity of Operators

Understand Python operator associativity rules, including left-to-right evaluation for most operators and exceptions like exponentiation (**) and assignment (=) which use right-to-left associativity.

Precedence and Associativity are characteristics that determine how the Python interpreter should evaluate expressions.

The combination of values, variables, operators, and function calls is termed as an expression. The Python interpreter can evaluate a valid expression.

Precedence of Python Operators

The precedence of operators in Python is shown in the following table in descending order (i.e., higher rows have higher priority than lower rows)

Operators Description
() Parentheses
** Exponent
+x, -x, ~x Unary plus, Unary minus, Bitwise NOT
*, /, //, % Multiplication, Division, Floor division, Modulus
+, - Addition, Subtraction
<<, >> Bitwise shift operators
& Bitwise AND
^ Bitwise XOR
&124; Bitwise OR
==, !=, >, >=, <, <=, is, is not, in, not in Comparisons, Identity, Membership operators
not Logical NOT
and Logical AND
or Logical OR
=
+= -=
*= /=
%= &=
^= &124;=
<<= >>=		 Assignment
Addition/subtraction assignment
Multiplication/division assignment
Modulus/bitwise AND assignment
Bitwise exclusive/inclusive OR assignment
Bitwise shift left/right assignment

Examples

Precedence of + and *

expr = 10 + 20 * 30
print(expr) # 610

Precedence of AND, OR and parenthesis ()

a = "ok"
b = 10

print(a == "ok" or a == "oook" and b>=15)   # True
print((a == "ok" or a == "oook") and b>=15) # False

Associativity of Python Operators

Groups of operators in the same rows in the previous table have the same precedence.

Associativity makes it possible to determine the order of operations that have the same precedence.

Associativity is the order in which an expression is evaluated that has multiple operators of the same precedence.

This table lists all operators from the highest precedence to the lowest precedence with associativity

Operator Description Associativity
( ) Parentheses left-to-right
** Exponent right-to-left
* / % Multiplication/division/modulus left-to-right
+ - Addition/subtraction left-to-right
<< >> Bitwise shift left, Bitwise shift right left-to-right
< <= > >= Relational less than/less than or equal to Relational greater than/greater than or equal to left-to-right
== != Relational is equal to/is not equal to left-to-right
is, is not, in, not in Identity
Membership operators		 left-to-right
& Bitwise AND left-to-right
^ Bitwise exclusive OR left-to-right
&124; Bitwise inclusive OR left-to-right
not Logical NOT right-to-left
and Logical AND left-to-right
or Logical OR left-to-right
=
+= -=
*= /=
%= &=
^= &124;=
<<= >>=		 Assignment
Addition/subtraction assignment
Multiplication/division assignment
Modulus/bitwise AND assignment
Bitwise exclusive/inclusive OR assignment
Bitwise shift left/right assignment		 right-to-left

For examples:

print(5 * 2 // 3) # 3
print(5 * (2 // 3)) # 0

print(2 ** 3 ** 2) # 512 (Since 2**(3**2) = 2**9

print((2 ** 3) ** 2) # 64

Non associative operators

Some operators, like assignment operators and comparison operators, do not have associativity in Python.

For example, x < y < z means neither (x < y) < z nor x < (y < z). x < y < z is equivalent to x < y and y < z, and is evaluated from left to right.

x = y = z = 1
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